[CI] Properly use Yoga u-c everywhere

Follow-up to [1].
This unbreaks CI which was broken by a recent change to
master upper-constraints. [2]

[1] I82c4ff3b246c7db65ac8660b096d4a9a15dda8d7
[2] https://review.opendev.org/c/openstack/requirements/+/843722/3/upper-constraints.txt#b244

Change-Id: Idc7a893f53c6975cc4a3f6090020d973fa2288bb

tests/run.yml

@@ -588,7 +588,7 @@
         - name: checkout the current requirements branch
           shell:
             cmd: |
-              git checkout {{ zuul.branch }}
+              git checkout {{ zuul.projects["opendev.org/openstack/requirements"].checkout }}
               echo "requirements checked out to:"
               git log --pretty=oneline  -1
             chdir: "{{ ansible_env.HOME }}/src/opendev.org/openstack/requirements/"

zuul.d/base.yaml

@@ -249,7 +249,8 @@
     run: tests/run-hashi-vault.yml
     required-projects:
       - openstack/kolla-ansible
-      - openstack/requirements
+      - name: openstack/requirements
+        override-checkout: stable/yoga
     voting: false
     irrelevant-files:
       - ^.*\.rst$